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Characterization of mesoporous silica thin films for application to thermal isolation layer
Lee, Junmyung,Kim, Jihun,Lee, Byung Jun,Lee, Jongchan,Lee, Hyun Woo,Hong, Min-Hee,Park, Hyung-Ho,Shim, Dong Il,Cho, Hyung Hee,Kwon, Kwang-Ho Elsevier 2018 THIN SOLID FILMS - Vol.660 No.-
<P><B>Abstract</B></P> <P>Mesoporous silica thin films were easily prepared by a sol–gel process and spin-coating, and the film properties were investigated for potential application to thermal isolation layers. Scanning electron microscopy and X-ray diffraction were used to determine the film thicknesses and to analyze the mesoporous film structures, respectively. The refractive indexes and porosities of the films were determined by spectroscopic ellipsometry and the Lorentz–Lorenz equation, respectively. The infrared absorptions and thermal conductivities of the films were measured by Fourier transform infrared spectroscopy and a 3-ω method, respectively. The porosity and the number of pores of the films increased with increasing Brij-76 surfactant concentration, the interpore distance and thermal conductivity decreased. The experimental results showed that the mesoporous silica thin films could be function as excellent thermal isolation layers.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We have studied the characteristics of mesoporous silica thin films. </LI> <LI> Mesoporous silica films were fabricated by a sol gel process and spin coating. </LI> <LI> Properties of surfactant concentration and thin film thickness were investigated. </LI> </UL> </P>
Lee, Dong Jin,Lee, Hongkyung,Ryou, Myung-Hyun,Han, Gi-Beom,Lee, Je-Nam,Song, Jongchan,Choi, Jaecheol,Cho, Kuk Young,Lee, Yong Min,Park, Jung-Ki American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.22
<P>Mesoporous silicon nanofibers (m-SiNFs) have been fabricated using a simple and scalable method via electrospinning and reduction with magnesium. The prepared m-SiNFs have a unique structure in which clusters of the primary Si nanoparticles interconnect to form a secondary three-dimensional mesoporous structure. Although only a few nanosized primary Si particles lead to faster electronic and Li<SUP>+</SUP> ion diffusion compared to tens of nanosized Si, the secondary nanofiber structure (a few micrometers in length) results in the uniform distribution of the nanoparticles, allowing for the easy fabrication of electrodes. Moreover, these m-SiNFs exhibit impressive electrochemical characteristics when used as the anode materials in lithium ion batteries (LIBs). These include a high reversible capacity of 2846.7 mAh g<SUP>–1</SUP> at a current density of 0.1 A g<SUP>–1</SUP>, a stable capacity retention of 89.4% at a 1 C rate (2 A g<SUP>–1</SUP>) for 100 cycles, and a rate capability of 1214.0 mAh g<SUP>–1</SUP> (at 18 C rate for a discharge time of ∼3 min).</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-22/am403798a/production/images/medium/am-2013-03798a_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am403798a'>ACS Electronic Supporting Info</A></P>
Resource Allocation with QoS Supporting in Macro-Femtocell Networks
Jongchan Lee,Moonho Lee 보안공학연구지원센터 2015 International Journal of Multimedia and Ubiquitous Vol.10 No.1
The macro-femto overlaid LTE-Advanced networks have been drawing many attentions from mobile operators with their capability of extending coverages and supporting higher data rates. Effective and efficient resource allocation schemes must be preceded in order to deploy this overlaid cellular network successfully. This paper proposes the adaptive resource management scheme which categorizes the entire time-frequency resource blocks of the overlaid cellular network into the dedicated and the shared one, and allocates these resources stage by stage on the basis of user location and user-required data rate in order to expand the user accommodation capacity. Moreover, it enables to share loads evenly in the overlaid cellular network by performing cross-tier handovers from the macrocell to the femtocell so as to maximize the total packet throughput to a certain degree. We used a simulation to evaluate the effectiveness of our scheme with the performance measure of the outage probability and total packet throughput.
Lee, Jongchan,Jung, Woo Young,Lee, Hyun Chul,Kim, Gyu Tae,Lee, Doo Yong Elsevier 2018 Annals of nuclear energy Vol.114 No.-
<P><B>Abstract</B></P> <P>Scrubber nozzles are key pieces of equipment used to remove aerosols in a wet-type filtered containment venting system (FCVS). This study deals with the aerosol scrubbing efficiency of a scrubber nozzle operating in self-priming mode. The scrubber nozzle that has been developed in this work consists of a reducer, a throat, a diffuser, a liquid suction slit, and an end cap with a rectangular section area. The aim of this study was to characterize scrubbing efficiency under various thermal hydraulic and aerosol conditions including nozzle inlet pressure (250–600 kPa(g)), nozzle inlet temperature (102–164 °C), nozzle inlet flow rate (air: 42–132 m<SUP>3</SUP>/h, steam: 112–269 m<SUP>3</SUP>/h), submergence from the nozzle exit (0.7–2.7 m), aerosol size (0.5, 0.7, 3 µm), nozzle inlet aerosol concentration (0.1–3 g/m<SUP>3</SUP>), and steam mass fraction in the main carrier gas (0–1). Aerosol scrubbing efficiency was measured based on the inlet and outlet aerosol concentrations of the scrubbing vessel with isokinetic sampling systems including a glass microfiber filter. Experimental results show that the scrubbing efficiency increased with increasing aerosol size, steam mass fraction, nozzle submergence, and inlet aerosol concentration. We also showed that the scrubbing efficiency increased with an increase in inlet pressure at low scrubber nozzle submergence. However, at higher scrubber nozzle submergence, the nozzle inlet pressure did not significantly influence the scrubbing efficiency. The aerosol scrubbing efficiency with the developed self-priming scrubber nozzle submerged in the pool was over 97% for various thermal–hydraulic conditions. Thus, the experimental results can be used to design a wet scrubber system considering upstream conditions such as operation of the FCVS.</P>
Polysulfide rejection layer from alpha-lipoic acid for high performance lithium-sulfur battery
Song, Jongchan,Noh, Hyungjun,Lee, Hongkyung,Lee, Je-Nam,Lee, Dong Jin,Lee, Yunju,Kim, Chul Hwan,Lee, Yong Min,Park, Jung-Ki,Kim, Hee-Tak The Royal Society of Chemistry 2015 Journal of Materials Chemistry A Vol.3 No.1
<P>The polysulfide shuttle has been an impediment to the development of lithium-sulfur batteries with high capacity and cycling stability. Here, we report a new strategy to remedy the problem that uses alpha-lipoic acid (ALA) as an electrolyte additive to form a polysulfide rejection layer on the cathode surface<I>via</I>the electrochemical and chemical polymerization of ALA and a stable solid electrolyte interface (SEI) layer on the Li metal anode during the first discharge. The poly(ALA) layer formed<I>in situ</I>effectively prevents the polysulfide shuttle and consequently enhances the discharge capacity and cycling stability, owing to the Donnan potential developed between the polysulfide-concentrated cathode and the fixed negative charge-concentrated poly(ALA) layer. Also, the SEI layer additionally prevents the chemical reaction of the polysulfide and Li metal anode. The approach, based on the double effect, encompasses a new scientific strategy and provides a practical methodology for high performance lithium-sulfur batteries.</P>
고성능 리튬 설퍼 전지 구현을 위한 폴리설파이드 억제막
( Hee-tak Kim ),( Jongchan Song ),( Hyungjun Noh ),( Hongkyung Lee ),( Je-nam Lee ),( Dong Jin Lee ),( Yunju Lee ),( Chul Hwan Kim ),( Yong Min Lee ),( Jung-ki Park ) 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
The polysulfide shuttle has been an impediment to the development of lithium-sulfur batteries with high capacity and cycling stability. Here, we report a new strategy to remedy the problem that uses alpha-lipoic acid (ALA), as an electrolyte additive to form a polysulfide rejection layer on the cathode surface via the electrochemical and chemical polymerization of ALA during the first discharge. The poly(ALA) layer formed in situ effectively prevents the polysulfide shuttle and consequently enhances the discharge capacity and cycling stability, owing to the Donnan potential developed between the polysulfide-concentrated cathode and the fixed negative charge-concentrated poly(ALA) layer. The approach, based on a thermodynamic equilibrium and a natural material, encompasses a new scientific strategy and provides a practical methodology for high performance lithium-sulfur batteries.